The present invention relates to an arrangement in connection with a lighting fixture, the arrangement comprising a first light source arranged in connection with the lighting fixture structure.
In several objects of use of lighting fixtures, adaptability is required of the lighting according to the particular lighting needs and possibly changing conditions. This is the case for instance in public transport vehicles, such as buses, trains and trams, where the level of lighting is adjusted in accordance with generally changing conditions and to make passengers feel more comfortable.
Also inside buildings it is often recommendable to be able to dim the lighting without darkening the particular space completely. Such is the case for example in various serviced flats and the like, where there must always be some kind of lighting in the corridors.
In public transport vehicles, the lighting in the passenger cabin is adjusted for instance in such a way that when the external lighting decreases, the level of lighting in the passenger cabin is lowered, so that the contrast between the lighting conditions outside the vehicle and inside it would not disturb passengers. Dimmed lighting also creates better conditions for sleeping in the passenger cabin. During dimmed lighting, it is typically possible for the passengers to use personal reading lamps, if desired.
Decreasing the lighting is also applied when a vehicle is transported without passengers. In such a case, it is unnecessary to maintain full lighting in the passenger cabin, but for the sake of the driver's safety and the passengers' comfort, there is a reason to maintain some lighting in the passenger cabin.
Presently, decreasing the lighting is implemented in vehicle passenger cabins by using lamps that can be dimmed. A dimming function becomes possible for instance by using fluorescent lamps, the actuator of which is an electronic ballast. Using such a ballast allows the lighting provided with a fluorescent lamp to be dimmed steplessly up to a certain level. However, the minimum lighting provided with fluorescent lamps is in the order of 2 to 5% of the ordinary lighting level of the lamp, this minimum level being often too strong to be comfortable, in particular during dark times. Further, the overall efficiency of fluorescent lighting is significantly reduced because of dimming, whereby, however, the energy consumption for example at a lighting level of 5% is as much as 30% of the ordinary level due to the additional equipment and heater circuits required for the burning of a fluorescent lamp.
Another option to decrease lighting in passenger cabins is to use only a part of the passenger cabin lamps. Partial use of lamps causes, however, uneven distribution of light, there being apparent differences in lighting in different parts of the passenger cabin. Further, partial use of lamps consumes the lamps used for lighting unevenly and causes thus additional maintenance costs.
U.S. Pat. No. 5,647,658 discloses a fiber-optic lighting system for aircrafts. In the system of the publication, fiber-optic cables are used alone for lighting an aircraft cabin. Light is supplied to the fibers by using a high-intensity lamp, and the lighting provided by the fibers is used as the general lighting of the aircraft.